hi j
I sadly do not have any explanation why the 10k mode does not show up. generally a mode will not show up if it does not get get excited or may not radiate sound (eg mic is in a null). Alternatively, the mode can disappear or get high dampened. however, I cannot explain how that could happen. as I recall, the 10k mode is around the inner part of the cone, dustcap and coil former. The 10k mode shows up in comsol as well.
cheers
Lars
I sadly do not have any explanation why the 10k mode does not show up. generally a mode will not show up if it does not get get excited or may not radiate sound (eg mic is in a null). Alternatively, the mode can disappear or get high dampened. however, I cannot explain how that could happen. as I recall, the 10k mode is around the inner part of the cone, dustcap and coil former. The 10k mode shows up in comsol as well.
cheers
Lars
Could it be temperature and humidity differences between erin's and your measurement situation?
Temperature can certainly affect TSP like Fs and Vas, and really drastically take out the response below 200Hz or so, and also affect the upper mids and treble, for sure. This has been documented elsewhere.
But to be clear, both measurements were done by Erin, in his climate controlled garage, with the Klippel NFS.
First, on the large baffle:
Second, mounted in my cabinet:
The difference around 1.2KHz may be difficult to determine with my measurement equipment which lacks the microscopic resolution of the NFS. But the 10KHz IS within the resolution of my equipment. I just need time, and motivation to “restore” the resonance.
But to be clear, both measurements were done by Erin, in his climate controlled garage, with the Klippel NFS.
First, on the large baffle:
Second, mounted in my cabinet:
The difference around 1.2KHz may be difficult to determine with my measurement equipment which lacks the microscopic resolution of the NFS. But the 10KHz IS within the resolution of my equipment. I just need time, and motivation to “restore” the resonance.
Last edited:
The 1.2 khz puzzle, i assume it is the "jump" in the large bffle case which does not show up in the box case.
A possible cause is that the mounting in the large baffle had a resonance there, should check the impedance measurement of that case. From a structural point of view the box is much stiffer, thus the driver "feels" more mass during transients (aka a better mechanical grounding if you will).
Wrt the 10khz spikes, what is the time difference between the 2 measurements? Could it be some glue joint that has become more stiff over time? The peak at 5.2 khz looks less "high" in the box case compared to the large baffle case. Some damping going on? Perhaps , while writing , it could also come from the enclosed air forming some form of impedance loading the cone?
A possible cause is that the mounting in the large baffle had a resonance there, should check the impedance measurement of that case. From a structural point of view the box is much stiffer, thus the driver "feels" more mass during transients (aka a better mechanical grounding if you will).
Wrt the 10khz spikes, what is the time difference between the 2 measurements? Could it be some glue joint that has become more stiff over time? The peak at 5.2 khz looks less "high" in the box case compared to the large baffle case. Some damping going on? Perhaps , while writing , it could also come from the enclosed air forming some form of impedance loading the cone?
Last edited:
I will have to get another cabinet, a bare MDF box, to surface mount the driver, and use no deadening, damping, or decoupling. In fact none of the elaborate or advanced construction techniques as outlined in his treatise: https://www.somasonus.net/box-construction-methods and remeasure.
Anyone know the specification off hand for the baffle that is recommended for the NFS when testing raw drivers?
@lrisbo How large/thick is your baffle and it is braced?
Is it mounted at its edges?
Give me some time my fellow speaker nerds. I’m sure we’ll get to the bottom of this and bring back all the resonances in all their glory!
@augerpro
If it is indeed due to the well built cabinet, I owe you more than another few 🍻🍺
Edit: essential correction “I will have to get”
Anyone know the specification off hand for the baffle that is recommended for the NFS when testing raw drivers?
@lrisbo How large/thick is your baffle and it is braced?
Is it mounted at its edges?
Give me some time my fellow speaker nerds. I’m sure we’ll get to the bottom of this and bring back all the resonances in all their glory!
@augerpro
If it is indeed due to the well built cabinet, I owe you more than another few 🍻🍺
Edit: essential correction “I will have to get”
Last edited:
Not exactly, but it doesn't have to be that big
https://audioxpress.com/article/directivity-measurement-of-in-wall-loudspeakers
I'm sure there is an better answer in their documents somewhere if you really want to know.
hi j
i agree with your thoughts. FEA shows that the 5k is mostly concentrated to the coil former, inner cone and dustcap. As you say, if a large enough surface radiates out of phase we can get a cancellation (zeros of the transfer function while the modes are the poles). The Newton forces go all the way through the basket to the box so if anything here radiates we can get a cancellation. Similarly, if the baske tto box interface allows the driver to free float then radiation is changed again. So pretty complex like the air plane.
I think that we many times get confused by by only looking at static analysis. The landing impact is more like a step function plus perhaps a delta function components. the stimulus has therefor a fair amount of high frequency energy which will trigger higher frequency modes that possibly can involve the whole aircraft body to a higher degree than the DC mode (static). Just speculation here since I have zero knowledge of aircraft engineering
So the energy follows the available paths. And if one blocks a path with rubber grommets f.i. the energy will take another path. Yet if one would form a ridgid connection with some substantial mass it will drain the energy. Is this a correct rephrasing? My background as naval architect is with ships and mainly submarines (the Dutch Walrus class, how to deal with "pulses" aka underwater explosions) , not quite an airplane, but i did follow a course on fea given by aircraft engineers.
https://www.urbandictionary.com/define.php?term=phwoah
Lost in translation, clearly.
What he said:
https://www.facebook.com/hificompas...5fFGd4HH8pXrcneTUPFHAJNfijRdv3pzpCa4m3dnxdizl
"Can't remember when I was so much wowed by my new loudspeakers. Hardly ever...🙂"
Lost in translation, clearly.
What he said:
https://www.facebook.com/hificompas...5fFGd4HH8pXrcneTUPFHAJNfijRdv3pzpCa4m3dnxdizl
"Can't remember when I was so much wowed by my new loudspeakers. Hardly ever...🙂"
Last edited: